scholarly journals Dynamics of Plasmodium vivax populations in border areas of the Greater Mekong sub-region during malaria elimination

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Yuling Li ◽  
Yubing Hu ◽  
Yan Zhao ◽  
Qinghui Wang ◽  
Huguette Gaelle Ngassa Mbenda ◽  
...  
Keyword(s):  
Plasmodium Vivax ◽  
Malaria Elimination ◽  
Border Areas

scholarly journals Evolution of Plasmodium vivax populations in border areas of the Greater Mekong Subregion during malaria elimination

2020 ◽  
Author(s):  
Yuling Li ◽  
Yubing Hu ◽  
Yan Zhao ◽  
Qinghui Wang ◽  
Huguette Gaelle Ngassa Mbenda ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Plasmodium Vivax ◽  
Malaria Elimination ◽  
Scale Up ◽  
Transmission Dynamics ◽  
Clinical Samples ◽  
Effective Population ◽  
Border Areas ◽  
Greater Mekong Subregion ◽  
International Border

Abstract Background: Countries within the Greater Mekong Subregion (GMS) of Southeast Asia have committed to eliminating malaria by 2030. Although malaria situation has greatly improved, Plasmodium vivax remains at international border regions. Therefore, to gain a better understanding of transmission dynamics, knowledge on the evolution of P. vivax populations after the scale-up of control interventions will guide more effective targeted control efforts. Methods: We investigated genetic diversity and population structures in 206 longitudinally collected P. vivax clinical samples in two international border areas at the China-Myanmar border (CMB, n=50 in 2004 and n=52 in 2016) and western Thailand border (n=50 in 2012 and n=54 in 2015). Parasites were genotyped using 10 microsatellite markers. Results: Despite intensified control efforts, genetic diversity in the four populations remained high (HE = 0.66-0.86). The proportions of polyclonal infections showed substantial decreases to 23.7 and 30.7% in the CMB and western Thailand, respectively, with corresponding decreases in the multiplicity of infection. Consistent with the shrinking map of malaria transmission in the GMS over time, there were also increases in multilocus linkage disequilibrium, suggesting of more fragmented and increasingly inbred parasite populations. There were considerable genetic differentiation and subdivision with the four tested populations. Various degrees of clustering were evident between the older parasite samples collected in 2004 at the CMB with the 2016 CMB and 2012 Thailand populations, suggesting some of these parasites had shared ancestry. In contrast, the 2015 Thailand population was genetically distinctive, which may reflect a process of population replacement. The moderately large effective population sizes and proportions of polyclonal infections highlight the necessity of further coordinated and integrated control efforts on both sides of the borders in the pursuit of malaria elimination. Conclusions: With enhanced control efforts on malaria elimination, P. vivax population in the GMS has fragmented into a limited number of clustered foci, but the presence of large P. vivax reservoirs still sustains genetic diversity and transmission. These findings provide new insights into P. vivax transmission dynamics and population structure in this area.

scholarly journals A retrospective analysis of malaria epidemiological characteristics in Yingjiang County on the China–Myanmar border

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fang Huang ◽  
Shi-Gang Li ◽  
Peng Tian ◽  
Xiang-Rui Guo ◽  
Zhi-Gui Xia ◽  
...  
Keyword(s):  
Plasmodium Vivax ◽  
Retrospective Analysis ◽  
Malaria Elimination ◽  
Case Detection ◽  
Migrant Population ◽  
Predominant Species ◽  
Surveillance And Response ◽  
Response Systems ◽  
Border Areas ◽  
Epidemiological Characteristics

AbstractYingjiang County, which is on the China–Myanmar border, is the main focus for malaria elimination in China. The epidemiological characteristics of malaria in Yingjiang County were analysed in a retrospective analysis. A total of 895 malaria cases were reported in Yingjiang County between 2013 and 2019. The majority of cases occurred in males (70.7%) and individuals aged 19–59 years (77.3%). Plasmodium vivax was the predominant species (96.6%). The number of indigenous cases decreased gradually and since 2017, no indigenous cases have been reported. Malaria cases were mainly distributed in the southern and southwestern areas of the county; 55.6% of the indigenous cases were reported in Nabang Township, which also had the highest risk of imported malaria. The “1–3–7” approach has been implemented effectively, with 100% of cases reported within 24 h, 88.9% cases investigated and confirmed within 3 days and 98.5% of foci responded to within 7 days. Although malaria elimination has been achieved in Yingjiang County, sustaining elimination and preventing the re-establishment of malaria require the continued strengthening of case detection, surveillance and response systems targeting the migrant population in border areas.

scholarly journals Evolution of Plasmodium vivax populations in border areas of the Greater Mekong Subregion during malaria elimination

2019 ◽  
Author(s):  
Yuling Li ◽  
Yubing Hu ◽  
Yan Zhao ◽  
Qinghui Wang ◽  
Huguette Gaelle Ngassa Mbenda ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Plasmodium Vivax ◽  
Malaria Elimination ◽  
Scale Up ◽  
Transmission Dynamics ◽  
Clinical Samples ◽  
Effective Population ◽  
Border Areas ◽  
Greater Mekong Subregion ◽  
International Border

Abstract BackgroundCountries within the Greater Mekong Subregion (GMS) of Southeast Asia have committed to eliminating malaria by 2030. Although malaria situation has greatly improved, Plasmodium vivax remains at international border regions. Therefore, to gain a better understanding of transmission dynamics, knowledge on the evolution of P. vivax populations after the scale-up of control interventions will guide more effective targeted control efforts. MethodsWe investigated genetic diversity and population structures in 206 longitudinally collected P. vivax clinical samples in two international border areas at the China-Myanmar border (CMB, n=50 in 2004 and n=52 in 2016) and western Thailand border (n=50 in 2012 and n=54 in 2015). Parasites were genotyped using 10 microsatellite markers. ResultsDespite intensified control efforts, genetic diversity in the four populations remained high (HE = 0.66-0.86). The proportions of polyclonal infections showed substantial decreases to 23.7 and 30.7% in the CMB and western Thailand, respectively, with corresponding decreases in the multiplicity of infection. Consistent with the shrinking map of malaria transmission in the GMS over time, there were also increases in multilocus linkage disequilibrium, suggesting of more fragmented and increasingly inbred parasite populations. There were considerable genetic differentiation and subdivision with the four tested populations. Various degrees of clustering were evident between the older parasite samples collected in 2004 at the CMB with the 2016 CMB and 2012 Thailand populations, suggesting some of these parasites had shared ancestry. In contrast, the 2015 Thailand population was genetically distinctive, which may reflect a process of population replacement. The moderately large effective population sizes and proportions of polyclonal infections highlight the necessity of further coordinated and integrated control efforts on both sides of the borders in the pursuit of malaria elimination. ConclusionsWith enhanced control efforts on malaria elimination, P. vivax population in the GMS has fragmented into a limited number of clustered foci, but the presence of large P. vivax reservoirs still sustains genetic diversity and transmission. These findings provide new insights into P. vivax transmission dynamics and population structure in this area.

Dynamics of Plasmodium vivax populations in border areas of the Greater Mekong Sub-region during malaria elimination

2020 ◽  
Author(s):  
Yuling Li ◽  
Yubing Hu ◽  
Yan Zhao ◽  
Qinghui Wang ◽  
Huguette Gaelle Ngassa Mbenda ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Differentiation ◽  
Plasmodium Vivax ◽  
Malaria Elimination ◽  
Malaria Incidence ◽  
Scale Up ◽  
Transmission Dynamics ◽  
Clinical Samples ◽  
Border Areas ◽  
International Border

Abstract Background Countries within the Greater Mekong Sub-region (GMS) of Southeast Asia have committed to eliminating malaria by 2030. Although the malaria situation has greatly improved, malaria transmission remains at international border regions. In some areas, Plasmodium vivax has become the predominant parasite. To gain a better understanding of transmission dynamics, knowledge on the changes of P. vivax populations after the scale-up of control interventions will guide more effective targeted control efforts. Methods This study investigated genetic diversity and population structures in 206 P. vivax clinical samples collected at two time points in two international border areas: the China-Myanmar border (CMB) (n=50 in 2004 and n=52 in 2016) and Thailand-Myanmar border (TMB) (n=50 in 2012 and n=54 in 2015). Parasites were genotyped using 10 microsatellite markers. Results Despite intensified control efforts, genetic diversity remained high ( H E = 0.66-0.86) and was not significantly different among the four populations ( P >0.05). Specifically, H E slightly decreased from 0.76 in 2004 to 0.66 in 2016 at the CMB and increased from 0.80 in 2012 to 0.86 in 2015 at the TMB. The proportions of polyclonal infections varied significantly among the four populations ( P < 0.05), and showed substantial decreases from 48.0% in 2004 to 23.7 at the CMB and from 40.0% in 2012 to 30.7% in 2015 at the TMB, with corresponding decreases in the multiplicity of infection. Consistent with the continuous decline of malaria incidence in the GMS over time, there were also increases in multilocus linkage disequilibrium, suggesting more fragmented and increasingly inbred parasite populations. There were considerable genetic differentiation and sub-division among the four tested populations. Temporal genetic differentiation was observed at each site ( F ST = 0.081 at the CMB and F ST = 0.133 at the TMB). Various degrees of clustering were evident between the older parasite samples collected in 2004 at the CMB with the 2016 CMB and 2012 TMB populations, suggesting some of these parasites had shared ancestry. In contrast, the 2015 TMB population was genetically distinctive, which may reflect a process of population replacement. Whereas the effective population size ( N e ) at the CMB showed a decrease from 4979 in 2004 to 3052 in 2016 with the infinite allele model, the N e at the TMB experienced an increase from 6289 to 10259. Conclusions With enhanced control efforts on malaria, P. vivax at the TMB and CMB showed considerable spatial and temporal differentiation, but the presence of large P. vivax reservoirs still sustained genetic diversity and transmission. These findings provide new insights into P. vivax transmission dynamics and population structure in these border areas of the GMS. Coordinated and integrated control efforts on both sides of international borders are essential to reach the goal of regional malaria elimination.

scholarly journals Outbreak Investigation of Plasmodium vivax Malaria in a Region of Guatemala Targeted for Malaria Elimination

2017 ◽  
pp. 15-0698
Author(s):  
Robert Cohen ◽  
Joel Sarceño Cardona ◽  
Eliana Solares Navarro ◽  
Norma Padilla ◽  
Lisette Reyes ◽  
...  
Keyword(s):  
Plasmodium Vivax ◽  
Malaria Elimination ◽  
Vivax Malaria ◽  
Outbreak Investigation ◽  
Plasmodium Vivax Malaria

scholarly journals Plasmodium vivax and Plasmodium falciparum at the Crossroads of Exchange among Islands in Vanuatu: Implications for Malaria Elimination Strategies

PLoS ONE ◽  
2015 ◽  
Vol 10 (3) ◽  
pp. e0119475 ◽  
Author(s):  
Chim W. Chan ◽  
Naoko Sakihama ◽  
Shin-Ichiro Tachibana ◽  
Zulkarnain Md Idris ◽  
J. Koji Lum ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Plasmodium Vivax ◽  
Malaria Elimination

scholarly journals Heterogeneity in response to serological exposure markers of recent Plasmodium vivax infections

2020 ◽  
Author(s):  
Jason Rosado ◽  
Michael T. White ◽  
Rhea J. Longley ◽  
Wuelton Monteiro ◽  
Marcus Lacerda ◽  
...  
Keyword(s):  
Plasmodium Vivax ◽  
Malaria Elimination ◽  
Antibody Responses ◽  
Blood Stage ◽  
Transmission Intensity ◽  
Low Transmission ◽  
Recent Exposure ◽  
High Transmission ◽  
Antibody Titers

AbstractBackgroundAntibody responses to serological markers of Plasmodium vivax infection have been shown to correlate with exposure, but little is known about the other factors which affect antibody responses in naturally infected people from endemic settings. To address this question, we studied IgG responses to novel serological exposure markers (SEMs) of P. vivax in three settings with different transmission intensity.MethodologyWe validated a panel of 34 SEMs in a Peruvian cohort with up to three years’ longitudinal follow-up using the Luminex® platform and compared results to data from cohorts in Thailand and Brazil. Linear regression models were used to characterize the association between antibody responses and age, the number of detected blood-stage infections during follow-up, and time since the last infection. Receiver Operating Characteristic (ROC) analysis was used to test the performance of SEMs to identify P. vivax infections in the last 9 months.Principal findingsAntibody titers were associated with age, the number of blood-stage infections, and time since last P. vivax infection in all three study sites. The association between antibody titers and time since last P. vivax infection was stronger in the low transmission settings of Thailand and Brazil compared to the high transmission setting in Peru. Of the SEMs tested, antibody responses to RBP2b had the highest performance of classifying recent exposure in all sites, with area under the ROC curve (AUC) = 0.83 in Thailand, AUC = 0.79 in Brazil, and AUC = 0.68 in Peru.ConclusionsIn low transmission settings, P. vivax SEMs can accurately identify individuals with recent blood-stage infections. In high transmission settings, the accuracy of this approach diminishes substantially. We recommend the application of P. vivax SEMs for use in low transmission settings pursuing malaria elimination, but they appear less useful in high transmission settings focused on malaria control.Author SummaryPlasmodium vivax still poses a threat in many countries due to its ability to cause recurrent infections. Key to achieving the goal of malaria elimination is the ability to quickly detect and treat carriers of relapsing parasites. Failing to identify this transmission reservoir will hinder progress towards malaria elimination. Recently, novel serological markers of recent exposure to P. vivax (SEM) have been developed and validated in low transmission settings. It is still poorly understood what factors affect the antibody response to these markers when evaluated in contrasting endemic contexts. To determine the factors that influence the antibody response to SEM, we compare the antibody levels in three sites with different transmission intensity: Thailand (low), Brazil (moderate) and Peru (high). In this study, we found that transmission intensity plays a key role in the acquisition of the antibody repertoire to P. vivax. In highly endemic sites, the immunological memory resulting from a constant and sustained exposure will impact the performance of SEMs to detect individuals with recent exposure to P. vivax. In summary, SEMs that perform well in low transmission sites do not perform as well in high transmission regions.

scholarly journals Population genomics of Plasmodium vivax in Panama to assess the risk of case importation on malaria elimination

2020 ◽  
Vol 14 (12) ◽  
pp. e0008962
Author(s):  
Lucas E. Buyon ◽  
Ana Maria Santamaria ◽  
Angela M. Early ◽  
Mario Quijada ◽  
Itza Barahona ◽  
...  
Keyword(s):  
Plasmodium Vivax ◽  
Malaria Elimination ◽  
Population Genomics ◽  
Malaria Incidence ◽  
Malaria Prevalence ◽  
Human Migration ◽  
Parasite Population ◽  
Major Barrier ◽  
Travel History ◽  
Imported Cases

Malaria incidence in Panama has plateaued in recent years in spite of elimination efforts, with almost all cases caused by Plasmodium vivax. Notwithstanding, overall malaria prevalence remains low (fewer than 1 case per 1000 persons). We used selective whole genome amplification to sequence 59 P. vivax samples from Panama. The P. vivax samples were collected from two periods (2007–2009 and 2017–2019) to study the population structure and transmission dynamics of the parasite. Imported cases resulting from increased levels of human migration could threaten malaria elimination prospects, and four of the samples evaluated came from individuals with travel history. We explored patterns of recent common ancestry among the samples and observed that a highly genetically related lineage (termed CL1) was dominant among the samples (47 out of 59 samples with good sequencing coverage), spanning the entire period of the collection (2007–2019) and all regions of the country. We also found a second, smaller clonal lineage (termed CL2) of four parasites collected between 2017 and 2019. To explore the regional context of Panamanian P. vivax we conducted principal components analysis and constructed a neighbor-joining tree using these samples and samples collected worldwide from a previous study. Three of the four samples with travel history clustered with samples collected from their suspected country of origin (consistent with importation), while one appears to have been a result of local transmission. The small number of Panamanian P. vivax samples not belonging to either CL1 or CL2 clustered with samples collected from Colombia, suggesting they represent the genetically similar ancestral P. vivax population in Panama or were recently imported from Colombia. The low diversity we observe in Panama indicates that this parasite population has been previously subject to a severe bottleneck and may be eligible for elimination. Additionally, while we confirmed that P. vivax is imported to Panama from diverse geographic locations, the lack of impact from imported cases on the overall parasite population genomic profile suggests that onward transmission from such cases is limited and that imported cases may not presently pose a major barrier to elimination.

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